Excessive valve seating impact velocity is a problem familiar to many hydraulic system designers. In many modern applications, high speed hydraulic valves and related components may reciprocate many times per second. In order to generate such rapid action, the system components are often driven with relatively high forces. When a valve impacts its seat at too high a velocity, the seat and/or the valve itself can be damaged, compromising the sealing ability of the valve and in some instances rendering the valve inoperable.
A gas exchange valve in an internal combustion engine typically moves rapidly back and forth between an open position for intake or exhaust strokes, and a closed position during compression and power strokes. Repeated impacts of the valve against its seat can deform, break or otherwise damage the components, causing gases to leak past the valve seat when closed or worse, breaking the valve altogether. Disruptions in gas exchange during engine operation can result in sub-optimal engine performance. In more exotic engine operation schemes, proper valve seating can be critical to achieving a desired engine performance.
Valve “snubbers” are a class of hydraulic apparatuses addressing problems similar to those discussed above. Snubbing devices of varying complexity have been developed over the years. However, the small, rapidly moving hydraulic parts from some known systems must often be machined to very close tolerances, making mass production challenging and expensive. Moreover, during cold start conditions it can be difficult to initiate operation of a hydraulic system having numerous small parts bathed in cold, viscous oil.
One snubber system is known from U.S. Pat. No. 5,577,468 to Weber. Weber describes a hydraulic snubber for controlling engine valve seating velocity. In the Weber design a plunger is operably coupled to a gas exchange valve in an engine, and reciprocates in a housing between an advanced position and a retracted position. Weber's snubber includes a machined plate positioned above the plunger and having a first position during extension of the plunger, and a second position during retraction of the plunger. In the snubber plate's first position, it allows actuation fluid to be delivered to the plunger through a set of passages having a given flow area, whereas in the snubber's second position it restricts the available flow area to a single, relatively smaller passage for evacuation of actuation fluid. The smaller flow path determined by the position of the plate appears to slow the plunger as it approaches a seat, also reducing the seat impact velocity of the valve member coupled to the plunger.
Although the Weber design is believed to function effectively there is always room for improvement. In particular, Weber requires a relatively large number of parts for its snubber assembly.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.